FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
High tenacity polyester fibers and filament yarns
APPLICANTS
Reliance Industries Limited, 5th Floor, Maker Chamber IV, Nariman Point, Mumbai 400 021, Maharashtra, India, An Indian company
INVENTORS
Mukhopadhyay Anjan Kumar, A-1202/ Pride Plot no.l, Sector 7 Kharghar Navi Mumbai 410210, Krishnamurthy Gurudatt, No. 12, pattatreya road, Basavanagudi, Bangalore 560 004, Nadkarni Vikas Madhusudan, A18 Garden Estate, Off DP Road, Aundh,Pune -411007, Maharashtra India and Wadekar Shreeram Ashok, 204, Mohandeep Co-Op Housing Society Ltd., Almeida Road, Chandanwadi, Panchpakhadi, Thane (West),400601, Maharashtra, India, all Indian nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention is directed to polymeric materials, more particularly, to polyester fibers and filament yarns which exhibit high tenacity and low shrinkage.
BACKGROUND
High tenacity polyester fiber and filament yarn is a product in great demand for specific downstream applications. Apart from high tenacity, retention of tenacity after dyeing (a process of coloration) is also critical. Rigidity of structure is known to govern the level of shrinkage during dyeing. If sufficient rigidity is not attained during the heat-setting step of fiber processing, fibers and/or filament yarn may suffer from high shrinkage during downstream processing such as dyeing.
Another approach to meet targets of tenacity and shrinkage is based on drawline process optimization which results in lowering of productivity. The only option to overcome this productivity loss is hardware changes, which involves large space requirement and huge investments. Other approach of using higher molecular weight polymer presents its own set of problems during spinning and drawline. Yet another approach of solid-state polymerization of yarns produced, adds a costly step to the process.
EP526740 discloses use of adipic acid to make polyester yarn with high strength, high modulus and low heat shrinkage.

US6759124 discloses use of sodium benzoate in combination with thermoplastic polymer like polypropylene to get low-shrink, high tenacity, and extremely high modulus levels in the fibers.
US7662877 discloses use of adipic acid and sodium benzoate added to polyethylene terphthalate (PET) to impart clarity and transparency. The PET resin is bottle grade having IV in the range of 0.93-0.97.
The present inventors have unexpectedly found that the combination of adipic acid and sodium benzoate exhibits a surprising, synergistic effect in increasing the tenacity of polyester fibers/filaments at lower elongation values. The desired extent of improvement in tenacity could not be obtained with the individual use of the additives.
DESCRIPTION OF THE INVENTION
The present invention relates to a thermoplastic polyester fiber or filament yarn comprising synergistically effective amount of adipic acid as co-monomer and sodium benzoate as nucleating agent, wherein adipic acid co-monomer is present in at least 0.5 wt% based on weight of polyester and sodium benzoate has a mass of at least 5 ppm based on weight of polyester.

Another aspect of the invention relates to a process for the preparation of high tenacity thermoplastic polyester fiber or filament yarn composition comprising the steps of
1) Polymerisation of terphthalic acid and monoethylene glycol in presence of at least 0.5 wt% adipic acid and at least 5 ppm sodium benzoate by esterifi cation and .poly condensation to obtain molten polymer; and
2) Melt Spinning of the molten polymer obtained in step 1.
BREIF DESCRIPTION OF DRAWING
Fig. 1 illustrates a lab scale demonstration of oriented crystallization for fiber with additive and without additive.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or -step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or
steps.
An embodiment of the present invention relates to a thermoplastic polyester fiber or filament yarn comprising synergistically effective amount of adipic acid and sodium benzoate, wherein adipic acid co-monomer is present in at least 0.5 wt%

based on weight of polyester and sodium benzoate is having a mass of at least 5 ppm based on weight of polyester.
The combination of adipic acid as co-monomer and sodium benzoate as a nucleating agent collectively and synergistically imparts properties of high tenacity and low shrinkage to the polyester fiber or filament yarn.
In an embodiment of the invention, 2 wt% of adipic acid co-monomer is present based on weight of polyester and 100 ppm sodium benzoate is present based on weight of polyester.
In an embodiment of the invention, the thermoplastic polyester is made from terphthalic acid and monoethylene glycol.
The polyester fibers and/ or filament yarn produced exhibit higher tenacity and lower shrinkage, as compared to unmodified polyester fibers and/or filament yarns. The development is demonstrated without sacrificing the line speed. The polymers are prepared with specific additives that enhance the setting process of the polymer during the heat setting process. This effectively provides rigidity to the product, fibers and/or filament yarn.

Another embodiment- of the invention relates to a process for the preparation of high tenacity thermoplastic polyester fiber or filament yarn composition comprising the steps of
1) Polymerisation of terephthalic acid and monoethylene glycol in presence of at least 0.5 wt% adipic acid and at least 5 ppm sodium benzoate by esterification and poly condensation to obtain molten polymer; and
2) Spinning of the molten polymer obtained in step 1.
In a further embodiment, the melt spun polymer thus obtained can optionally be subjected to drawing, annealing, crimping, cutting and baling
The invention relates to a process for the preparation of high tenacity thermoplastic polyester fiber or filament yarn composition comprising the steps of
1) Polymerisation of terephthalic acid and monoethylene glycol in presence of at least 0.5 wt% adipic acid and at least 5 ppm sodium benzoate by esterification and poly condensation to obtain molten polymer;
2) converting the molten polymer into chips;
3) Drying and Crystallisation of the chips ; and
4) Melt Spinning of polymer chips obtained in step 3.
In a further embodiment, the melt spun polymer thus obtained can be subjected to drawing, annealing, crimping, cutting and baling.

Fig. 1 illustrates a lab scale demonstration of oriented crystallization for fiber with additive and without additive. The process conditions were similar for the two samples. The graph for fiber with the adipic acid additive shows sharper crystalline peaks in wide angle X-ray diffraction than for fibers without adipic acid additive. The sharpening of peaks corresponding to 110 plane at 2θ=22.5 and 010 plane at 20=17.0 are evident in the wide angle X-ray diffraction pattern. This confirms the initiation of crystallization in presence of adipic acid, while under similar conditions the fibers without adipic acid do not show significant crystallisation.
The key benefits of the present invention include
• Higher tenacity and lower shrinkage
• No lowering of productivity
• No need for hardware changes
• Low additional cost due to additives used
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the

purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Examples
The following experimental examples are illustrative of the invention but not limitative of the scope thereof.
Example 1 The thermoplastic polyester fiber or filament yam made from terephthalic acid and monoethylene glycol comprises
•Purified terephthalic acid / Monoethylene Glycol (mole ratio 1:2) •Antimony trioxide catalyst: 250 ppm Sb based on weight of polyester •Ti02; 0.05 wt% based on weight of polyester •Phosphoric acid: 20,.ppm as P based on weight of polyester • NaOH : 25 ppm based on weight of polyester •Adipic acid: 2 wt% based on t weight of polyester •Sodium benzoate : 100 ppm based on weight of polyester
Polymerization was carried out in a 50 kg batch reactor. Adipic acid was added in esterifier and equal amount of terphthalic acid reduced. Additive sodium benzoate was added at the end of esterification as a premix with hot EG. Target IV at the

end of polymerization was at least 0.6d 1/g. The key process conditions used are as detailed in table 1.
Table 1

Process Without adipic Adipic acid Adipic acid (2%)
Parameters acid and sodium (2%) + Sodium
benzoate Benzoate 100 ppm
Esterification 258.0 258.0 258.0
temperature (°C)
Esterification time 232 226 234
(min)
Poly condensation 120 118 113
time (min)
Poly condensation 285.4 285.2 285.0
temperature (°C)
Final 0.56 0.55 0.53
vacuum (mm Hg)
Final rpm (rpm) 950 . 950 950
Fully drawn yarns were produced from the different batches made with various combinations of adipic acid and sodium benzoate, as mentioned below, using pilot spinning machine with the following process conditions.

Chips drying temperature: 160°C Chips drying time: 4 hrs Extruder temperature: 285°C Throughput: 31.7 g / min / position Winding speed: 3800 mpm Draw ratio: 2.8 Yarn: 75 denier / 36 filaments Godet temperatures: 100°C
Evaluation of the yarns were done for tenacity and elongation on a tensile tester (Instron) using standard test procedure. Reduction in elongation% is used as a measure of lowering of shrinkage of fibres. Under the conditions used in the example, a lower elongation is reflective of facilitation of stabilization of structure by way of crystallization, which minimizes further shrinkage of fibres. The results of yarn properties are detailed in Table

Table 2

Additives (wt %) Tenacity (grams per denier) Elongation %
NIL 3.02 55.8
2% Adipic acid 4.05 21.5
2% Adipic acid + 5 ppm sodium benzoate 3.3 38.3
2% Adipic acid + 25 ppm sodium benzoate 3.5 45.2
2% Adipic acid + 50 ppm sodium benzoate 3.7 39.5
2% Adipic acid + 100 ppm sodium benzoate 4.23 23.0
2% Adipic acid + 200 ppm sodium benzoate 3.5 26.5
4% Adipic acid+50 ppm sodium benzoate 3.4 41.8
100 ppm sodium benzoate 4.00 33.4
4% Adipic acid 4.03 26.0
6% Adipic acid 3.4 32.9
At a level of adipic acid of 2%, there is progressive increase in tenacity with increased sodium benzoate levels upto 100 ppm levels. At higher than this level, tenacity is adversely affected. The data of 2% adipic acid and 100 ppm sodium benzoate, when compared with data for 2% adipic acid alone indicates that the tenacity had significantly gone up with the combination, which was not happening

with increase of adipic acid alone. This is indicative of synergistic effect of the combination of additives. In addition, the tenacity with 100 ppm of sodium benzoate alone also is lower than the combination. The elongation level at 100 ppm is also at higher level. This also validates that there is a synergistic effect of using this combination of adipic acid and sodium benzoate. Further, increasing adipic acid levels at a given sodium benzoate level has also not resulted in increase in tenacity. This indicates that there is a specific window of combination of the two additives, which will help in improving tenacity. This demonstrates the synergistic effect of these additives in achieving both high tenacity and low shrinkage, which is the objective of the present invention

We claim;
1. A thermoplastic polyester fiber or filament yarn comprising adipic acid and sodium benzoate wherein adipic acid is present in at least 0.5 wt% based on weight of polyester and sodium benzoate has a mass of at least 5 ppm based on weight of polyester.
2. The thermoplastic polyester fiber or filament yarn as claimed in claim 1. wherein 2 wt% of adipic acid is present based on weight of polyester.
3. The thermoplastic polyester fiber or filament yarn as claimed in claim 1, wherein 100 ppm sodium benzoate is present based on weight of polyester.
4. The thermoplastic polyester fiber or filament yarn as claimed in claim 1, wherein the polyester is made of terephthaiic acid & mono ethylene glycol.
5. The thermoplastic polyester fiber or filament yarn as claimed in claim 1, wherein
tenacity of fiber is atleast 3.3 gpd.
6. The thermoplastic polyester fiber or filament yarn as claimed in claim 1, wherein the intrinsic viscocity is not more than 0.64.

7. A process for preparation of thermoplastic polyester fiber or filament yarn
composition comprising the steps of
a) Polymerisation of terphthalic acid and monoethylene glycol in presence of at least 0.5 wt% adipic acid and at least 5 ppm sodium benzoate by esterification and poly condensation to obtain molten polymer; and
b) Spinning of the molten polymer obtained in step a).

8. The process for preparation of thermoplastic polyester fiber or filament yarn composition as claimed in claim 7, wherein polymerization is carried out in presence of 2 wt% of adipic acid.
9. The process for preparation of thermoplastic polyester fiber or filament yarn composition as claimed in claim 7, wherein polymerization is carried out in presence of 5 ppm sodium benzoate.
10. The process for preparation of thermoplastic polyester fiber or filament yarn composition as claimed in claim 7, wherein the process comprises direct spinning of the molten polymer obtained in step a.

11. The process for preparation of thermoplastic polyester fiber or filament yarn composition as claimed in claim 7, wherein the process comprises converting the molten polymer of step a) into chips, crystallization of said chips followed by melting and spinning into fibers thereof.